The crisis in Northern Ireland's political process over allegations of IRA intelligence gathering in the Northern Ireland Office is expected to reach a climax this week.

It follows a police raid on Sinn Fein's office at Stormont on Friday and the appearance in court of the party's head of administration at the Assembly.

Northern Ireland's main political parties held press conferences at Stormont setting out their positions.

Ulster Unionist leader and First Minister David Trimble accused Sinn Fein of a "massive political conspiracy" and the Northern Ireland Office of "massive incompetence" over the affair.

UUP leader David Trimble: "NIO incompetence"

"For a year, while we were meeting from time to time the secretary of state to discuss what might be done, in a situation where we met freely discussing on each side the tactics that might be adopted, Sinn Fein were reading the minutes of all those meetings.

"There has been political espionage on a massive scale and as far as one can see that espionage was directed by the republican movement for the purpose of aiding their political projects, their political tactics."

He added he wanted the British Government to take action and would delay his own action until he had met Prime Minister Tony Blair on Tuesday.

Sinn Fein President Gerry Adams said the raid on Sinn Fein's Stormont offices was "a piece of political theatre which was obviously aimed at tying not just Sinn Fein, but Sinn Fein's operation at this assembly, into whatever else was happening".

Sinn Fein president Gerry Adams: "Blame game"

"In my view this is because an element within the British system, working out that the institutions are likely to come down, are trying to ensure that if and when that happens, it will happen at a time and in a way that republicans get the blame."

He added: "We should not underestimate the fact that this process is in a crisis.

"When that crisis commenced, in my view, was at the Ulster Unionist Council meeting when that party opted into the anti-Agreement camp and decided to exit out of these institutions."

Democratic Unionist Party leader Ian Paisley said: "We are asking for an urgent debate on the motion that this house notes with great concern what has happened in this province over the last number of days so we can have a full blooded debate on this issue."

DUP leader Ian Paisley: "Agony must end"

He said until a debate was held his party would not take part in normal assembly business.

And he said he had filed a letter with the Speaker's office containing notice of the DUP ministers' resignation from the Northern Ireland Executive, to come into force immediately if Mr Trimble withdrew his ministers.

He said it would be outrageous if assembly members did not debate an issue which was under discussion in every home in Northern Ireland.

"The time has come that the blow has to be struck after four long years of agony."

SDLP leader and Deputy First Minister Mark Durkan said unionists were in danger of destroying the current political process.

SDLP leader mark Durkan: "Destruction"

"Unionist politicians have to be asked whether bringing the institutions down in these circumstances is actually going to give us any prospect of moving forward in the future.

"Using this as the latest excuse for destruction or disengagement is not actually offering the community, and the unionist community in particular, the leadership that is needed.

"This is a time when we as leaders need to do more than just pander to the moods that we know are out there."